Conventionally, as a device for cutting a work formed of a metal or the like, there is known a device configured to hold an end portion side of a tool holder with a cutting blade portion fixed to its leading end and to rotate this tool holder. Such device suffers a problem that when the blade portion on the leading end side comes into contact with a work, the tool holder is bent and deformed to cause vibration in the tool holder, thus leading to reduction in machining precision. Such vibration differs in its mode, depending on the length or outer dimensions of the tool holder or property of material constituting the tool holder, etc.
For this reason, e.g. Patent Document 1 shows a case in which for obtaining a large damping ratio for a wide range of vibration frequency, a boring bar for use in a boring operation is formed with using a plurality of layers of cylindrical members arranged coaxially with each other. According to a mechanism disclosed in this document, when a work is cut by this boring bar, the cutting force will be transmitted in the mutually engaged cylindrical members one after another to eventually reach a spindle. In the course of this, slight displacement will occur between the adjacent cylindrical members, thus causing friction between the multiple-layered members, which will dissipate the energy quickly.
Further, Patent Document 2 discloses a case in which a boring bar is constituted of a boring bar head connecting a leading end portion and a base end portion of the boring bar with a clamping bolt and a plurality of thin hollow bars that are arranged in multiple layers over the clamping bolt between the leading end portion and the base end portion. Around the outer circumferences of these thin hollow bars, an outer tube is provided, so that a screw or the like provided in this outer tube is used for fastening center portions of the thin hollow bars. With this fastening, the plurality of thin hollow bars arranged in the multiple layers are brought into contact with each other to generate a friction, which in turn absorbs vibration.